We have demonstrated growth retardation in a child with hereditary fructose intolerance (HFI) at levels of fructose ingestion that did not produce acute symptoms. Highly significant growth was achieved by fructose restriction. A protocol is presented to evaluate the possible role of disturbed adenine nucleotide metabolism and energy dissipation in abnormal growth in children with HFI. Evidence is presented suggesting that, in patients with HFI, fructose exposure induces dysfunction detectable by increased rates of lysosomal residual body excretion in the urine. If found, this dysfunction offers the possibility of heterozygote identification and the possibility of elucidation of pathogenetic mechanisms relevant to a broad range of metabolic diseases.